The present invention relates generally to voice storage and retrieval systems capable of providing speech synthesis, and move specifically to a voice storage and retrieval system of the type capable of reducing the burden of a controller that controls the synthesis of a voice response from stored voice segments.
FIG. 1 shows one prior art voice storage and retrieval system incorporated in a voice mail system. In this system, a synthesized voice is first generated from voice segments stored in a voice segment memory 4 and sent to a requesting subscriber to indicate a source mail box number and the date and time of day at which a voice message is recorded. Transmission of the synthesized voice is followed by the transmission of the recorded voice message which is stored in a hard disk 6. When reconstructing voice segments, a main controller 1 issues a request to an auxiliary controller 2 which responds to it by supplying a direct memory access (DMA) controller 3 with the addresses of voice segments in the memory 4 and other necessary information and by specifying one of a plurality of buffer memories 7. DMA controller 3 accesses voice segment memory 4 to read the addressed voice segments therefrom for transfer to the specified buffer memory. When retrieving a recorded voice message, main controller 1 issues a request to a disk controller 5 to read a recorded voice message from hard disk 6 and supplies it to the specified buffer memory where it is stored temporarily for later delivery to the requesting subscriber under control of the auxiliary controller in order to accommodate different transmission speeds among subscriber lines.
One disadvantage of this prior art system is that during the time the voice segments are being transferred to the buffer memory, the bus system of the auxiliary controller is exclusively occupied by the DMA controller 3 and the operating efficiency of the auxiliary controller is significantly reduced.